Techniques for soil or ground improvement include soil mixing, jet grouting, stone columns, vibro concrete columns, controlled modulus columns, and aggregate pier techniques. Soil mixing and jet grouting involve the enhancement of in situ soil with cement binders. Vibro stone column techniques were developed in the 1940s in Germany. Vibro concrete columns were a later extension of traditional stone columns. Controlled modulus columns were developed in France in the 1980s. Aggregate pier techniques were developed by Nathaniel S. Fox and his coworkers in the early 1990s as described by U.S. Pat. No. 5,249,892, titled “Short Aggregate Piers and Method and Apparatus for Producing Same,” and issued Oct. 5, 1993. Fox's technique involves the steps of drilling a hole in the ground, filling the hole incrementally with loose lifts of aggregate, and compacting the aggregate with a tamper head.
Fox also developed the “Impact Pier” technique which includes the steps of driving a hollow steel pipe in the ground, filling the pipe with aggregate stone, extracting the pipe in increments, and then advancing the pipe back downwards to compact the placed lift of aggregate in the ground. Advancements of the Impact technique include the use of grout or concrete, sometimes in a closed, pressurized system to construct a rigid cemented aggregate element. These aggregate or cemented-aggregate elements provide vertical support for foundations. Shortcomings exist between the interface of the rigid elements and the foundation.
These more rigid soil improvement systems including vibro concrete columns, grouted or concreted aggregate piers, controlled modulus columns, and others require an aggregate transfer pad constructed following element construction between the tops of the rigid element and the bottom of foundations. Accordingly, it is desired to provide improved techniques to enhance this critical interface and to provide other soil improvement techniques and systems.